simple. How many distinct ways can the letters in the word: MISSISSIPPI be arranged.

another one:

what is the units digit of 9^4321 power?

another one:

If Bob spends 4 hours to completely repair a roof, and Frank spends 6 hours to completely repair that same roof, how long would it take them to repair the roof together.

another one:

How many terminating zeros are in 4321!

just a little note guys. All of these are from past math competitions i have been in. Lets see if you guys can crack them.